Electric plug



y 1 3 A. CARLINO 2,158,691

v ELECTRIC PLUG Filed Sept. 25, 1956' kg Z1 5}; 64 7 INVENTOR Alexander Larlz'no am J. m/

7 ATTORNEY v Patented May 16, 1939 PATENT OFFICE ELECTRIC PLUG Alexander Cal-lino, Cleveland, Ohio Application September 23, 1936, Serial No. 102.2%

1 Claim.

while still plugged "in the socket, particularly inthe case of an electric curling iron, the insulation on the cord, at the point where it enters the plug, becomes frayed due to the twisting or torsional strains imparted thereto by such use. In time the bare wires may be exposed, causing a dangerous iire hazard and necessitating replacement of the cord.

One object of my invention is the provision of,

20 aswivel joint between the two parts of the plug assembly whereby the part connected with the cord may rotate freely about itslongitudinal axis and still remain in electrical contact with the stationary part of the plug. Another object of my 25 invention is a novel plug construction in which spring contact is maintained between the two contact points on the stationary and movable parts of the assembly. A still further object comprises means for breaking the electricalcircuit 30 upon separation of the two parts of the plug in such a manner that any arcing that occurs will take place inside the plug, thus eliminating the possibility of fire or shock.

Other objects and advantages will-be apparent as from the following detailed description and drawing of an embodiment oi my invention, in which:

Figure 1 is a longitudinal sectional view 40 Figure 2 is a transverse sectional view taken through the assembly on line 2-2 of Fig. 1.

Figure 3 is a plan view of the movable part of the plug. I o v Figure 4 is a transverse sectional view taken on 45 line 4-4 of Fig.1, and

Figure 5 is a longitudinal sectional view of a modiflcationof the stationary member.

Referring to Figs. 1 to 4, there is shown a member ID of insulating material provided with 50 a threaded metallic element Ii adapted to be screwed into a lamp or wall socket. Member in may be recessed, as at l2, and a portion ii'ot element ll bent into the recess to assist in holding the element in position. 55 One of the electrical contacts in member i opening I! in member l0 and slot IS in element ii. The extension may be soldered or otherwise secured to element Ii so as to form a good electrical connection.

At thecenter of member III is a recess I! adapted to receive the contact for the other side of the circuit. A guide and locking member is formed in the shape of a U in such a manner that the bottom of the U engages the bottom of recess l9, and the sides of the U engage a pair of opposite side walls of the recess. Adiacent the outer surface Ii 01' member l0 each arm of the U-shaped member 20 is bent in a reverse direction, as at 2-2, and extends part way into recess is where the ends 01' portions 22 are bent towards each other to form locking shoulders 20 23. Inside of member 20 and lying against the bottom and side walls thereof is an insulating member 2! which separates member 20 from a contact element 25. Said latter element is made of spring material and comprises a bottom wall 25 28 and arms 21. Openings are provided in members- 20 and 24, and wall 28 of element 25 is threaded, to receive a bolt 2! that holds the parts in assembled relation. Itwill be noted that the opening in member 20 is considerable larger in 30 diameter than the bolt,'so as to prevent contact between such member and the bolt. An insulating disc 291s positioned between an enlarged head 30 of bolt 28 and the turned over portion ii of contact element II to thereby separate the bolt from said element.

The movable or swivel member of the plugassembly comprises a block 32 of insulating material provided with an opening 33 receiving the two wire conduit or cord (not shown) connected to the electrical device. The-block is recessed at 34 to receive the bases of the contact prongs l5 and 38. Prong I! is formed with a base 31 and is assembled with block 32 in such a manner that the prong is positioned substantially the same distance from the longitudinal center line of the plug assembly as is the groove II. Prong it is cylindrical in shape-and is likewise formed with a base 38, but an extension 39 thereon positions the prong at the center of block 32. Bases 31, 8|, 0 and hence the prongs, are held in position by bolts or rivets 40, Ill which may either be secured into threadedholes in block 32 or assembled with the latter as it is being molded into the desired.

shape. The bases are provided with the usual 65.

threaded holes for bolts i by which'the ends oithecordareconnectedtothecontacts.

Connection between the two parts oi the plug assemblyis made by inserting prong ll between arms I! or member II until the locking shoulders 28 enter a circular groove 42 at theend oi the prong. Armsflnormallytendtospring towards each other, and in moving prong It into position the arms are iorced apart so that shoulders 28 are held in groove I!v by the tension in the arms. Bythetimetheprongislock'edinpositionthe extreme end thereoi has engaged arms 21 01 contact element II. Arms II also normally tend to spring towards each other, and are forced apart by the tapered end ll of the prong so that a good connection is assured by means of the inward pressureoiarmsl'l. Itwiilbenotedthatarmsfl are provided with arcuate wings I which serve to position prong ll centrally oi! the plug and guide it in place. Locking shoulders 23 'are shown recessed, as at 4|, to coniorm to curvature of prong It so as to partially surround the latter member.

As prong 38 passes between arms 22, and before it reaches contact ll, prong ll engages the outer surface oi spring ll. Further movement of prong ll towards member il compresses the spring it and provides an electric contact under spring pressure. It will thus be apparent from the above description that block I! is free to rotaterelativetomember ilwhileatalltimesa firm engagement between the contacts is maintained.

Inl'ig.5thereis shownastatlonarypartsimilar to member I. but with an end formed for use with a common slip-in type of socket. The member ll is provided with a groove ii and recusl2,thesameasgroove ll andrecess I! respectively of Fig. 1. Spring 83 is shown in its extended position since the movable halt oi' the plug is not. in place. Connection between the spring and oneside oithe live circuitinthebase socket is elected by means oi-an element I which passes through a slot in member I and projects a considerable distance beyond said member. Element I is bent at one end, as at II, to form a stop which engages spring it at the bottom of groove ii. Spring 3 is soldered or otherwise secured to the bent portion ll. llementllmaybesimplyandefiectivelysecuredin member ll by bending over a portion ll thereof trical engagement.

touch. Inthismanneraddedspxingactionis' given the arms when the movable prong It is pushed. in position, causing the locking shoulders 23 (Fig. '1) to snap into groove 42 to hold the parts locked together.

Thus it will be apparent that my invention pro vides a swivel joint between the two parts 0! the plug so that the part to which the 'cord is attached may rotate and thus relieve the cord irom twisting strains. Furthermore, the plug may advantageously be used in ceiling sockets since the locking means holds the assembly firmly together and prevents the movable member irorn dropping out. In addition the spring engagement of the contact members assures a good electrical connection. It will also be observed that in breaking the circuit, which is the time at which movable part of the assembly is withdrawn. In

this manner danger of shock or short circuit is still further reduced to a minimum.

While I have shown and described my invention in-conjunction with a plug adapted to be inserted into a lamp or wall socket, it will be understood that the stationary part of the assembly may be incorporated in a base socket or wall outlet so that it may be fixedly mounted in the wall. The movable part of the assembly would, in such case, cooperate directly with the outlet.

The terms and expressions which I have employed are used as terms 01' description and not or limitation, and I have no intention, in the use of such terms and expressions, oi excluding any equivalents oi the features shown and described or portions thereoi, but recognize that various modifications are possible within the scope oi the invention claimed.

What I claim is:

An electrical connector comprising a pair oi detachable members, one oi said members having a longitudinally disposed recess and a groove spaced from and surrounding said recess, a hellcal spring contact element in said groove, a contact element at the inner end of said recess, guiding means in said recess having a pairof longitudinally disposed arms, the other of said members having a pair or metallic prongs adapted to be inserted in said groove and recess and enllle said contact elements, said spring being adapted to exert outward pressure against one 01' said prongs. and means at the end of one of said armsadapted to enter a groove in the other of said prongs substantially simultaneously with the engagement of said other prong with its respective contact element to hold said members in elec- ALEXANDER CARLINO. I 

